Physiological and biochemical responses of the forage legume Trifolium alexandrinum to different saline conditions and nitrogen levels

• Published in: Journal of plant research 2016-05, Vol.129 (3), p.423-434
• Main Authors: Zouhaier, Barhoumi, Mariem, Maatallah, Mokded, Rabhi, Rouached, Aida, Alsane, Khaldoun, Chedly, Abdelly, Abderrazek, Smaoui, Abdallah, Atia
• Format: Article
• Language: English
• Subjects: Anatomy & physiology; Biochemistry; Biomass; Biomedical and Life Sciences; Enzyme Assays; Forage crops; Glutamate-Ammonia Ligase - metabolism; Growth rate; Legumes; Life Sciences; Magnesium; Minerals - analysis; Nitrate Reductase - metabolism; Nitrogen; Nitrogen - pharmacology; Photosynthesis; Photosynthesis - drug effects; Plant Biochemistry; Plant Ecology; Plant growth; Plant Leaves - drug effects; Plant Leaves - enzymology; Plant Physiology; Plant Roots - anatomy & histology; Plant Roots - drug effects; Plant Roots - enzymology; Plant Sciences; Plant Stems - anatomy & histology; Plant Stems - drug effects; Plant Stomata - drug effects; Plant Stomata - physiology; Plant Transpiration - drug effects; Regular Paper; Saline soils; Salinity; Salts; Sodium chloride; Sodium Chloride - pharmacology; Stomatal conductance; Stress, Physiological - drug effects; Trifolium - anatomy & histology; Trifolium - drug effects; Trifolium - growth & development; Trifolium - physiology; Water use; Water use efficiency
• ISSN: 0918-9440; 1618-0860
• DOI: 10.1007/s10265-016-0791-6

Salinity stress reduces plant productivity, but low levels of salinity often increase plant growth rates in some species. We herein describe the effects of salinity on plant growth while focusing on nitrogen use. We treated Trifolium alexandrinum with two nitrogen concentrations and salinity levels and determined growth rates, mineral concentrations, nitrogen use efficiency, photosynthesis rates, and nitrate reductase (NR, E.C. 1.6.6.1) and glutamine synthetase (GS, EC 6.3.1.2) activities. The T. alexandrinum growth rate increased following treatment with 100 mM NaCl in low nitrogen (LN) and high nitrogen (HN) conditions. Salt treatment also increased root volume, intrinsic water use efficiency, and nitrogen use efficiency in LN and HN conditions. These changes likely contributed to higher biomass production. Salinity also increased accumulations of sodium, chloride, and phosphate, but decreased potassium and calcium levels and total nitrogen concentrations in all plant organs independently of the available nitrogen level. However, the effect of salt treatment on magnesium and nitrate concentrations in photosynthetic organs depended on nitrogen levels. Salt treatment reduced photosynthesis rates in LN and HN conditions because of inhibited stomatal conductance. The effects of salinity on leaf NR and GS activities depended on nitrogen levels, with activities increasing in LN conditions. In saline conditions, LN availability resulted in optimal growth because of low chloride accumulation and increases in total nitrogen concentrations, nitrogen use efficiency, and NR and GS activities in photosynthetic organs. Therefore, T. alexandrinum is a legume forage crop that can be cultivated in low-saline soils where nitrogen availability is limited.